Yes, because of aspect ratio of produced screens of mobile devices. So if you intend to make game strictly for mobiles I suggest to set your project aspect ratio to 16:9.
4:3 is simply dead meat, not used since 2009.
16:9 is now most common aspect ratio for sold televisions and computer monitors and is also the international standard format of HDTV, Full HD, non-HD digital television and analog widescreen television.
More info on wikipedia:
http: // en.wikipedia.org / wiki / 16:9
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